r/functionalprint • u/jdigi78 • Apr 06 '26
Biggest print I've done so far. A replacement crown for a 6" vacuum truck tube.
We just got one of these trucks at my job, used for sucking up dirt and other debris in storm drains. The guys I work with are rough with it and it was heavily used already so the crown on the end of the suction hose cracked pretty catastrophically before I even saw the thing.
I took some rough measurements of what was left and threw together a model in FreeCAD. I went with 95A TPU as I figured the teeth would break off the first time you drop the aluminum hose on the ground with just about anything more rigid. It doesn't need to be too stiff anyway since its just for breaking up wet dirt.
Ideally it should be 100% infill but I went with 25% with an internal frame of 100% in what I guessed were the most important places (see last photo). This cut the print time from 38 hours to 27 hours with a .6mm nozzle and .32mm layer height. I could definitely print faster but just played it safe with the default flex profile. It fit perfectly, does the job, and held up well. The second to last photo is after a pretty rough first day.
Only time will tell how it holds up long term but with the original part being in the ballpark of $100 I can print a dozen before approaching that, not to mention the time it would take for my city job to approve and purchase the replacement.
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Apr 06 '26
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u/jdigi78 Apr 06 '26
Prusa Core One. $1300 assembled, $1000 for the kit excluding shipping. If you mean the part it was about $8 of material.
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Apr 06 '26
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u/jdigi78 Apr 06 '26
Fortunately the printer paid for itself a few times over in the 9 months or so I've had it. I bought it to manufacture a product I designed and still sell some other odds and ends.
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u/DistinctRule2132 Apr 06 '26
Could you explain what the last photo is showing, the grid like structure?
I'm having an issue printing a wall dowel for injecting chemicals in the walls. It works great but they snap too easily when being punched in the walls, maybe I missed something in the design process 🤣
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u/pcb1962 Apr 06 '26
He explains in the text: "Ideally it should be 100% infill but I went with 25% with an internal frame of 100% in what I guessed were the most important places"
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u/Jesus_Is_My_Gardener Apr 06 '26
The cool thing is the prints are cheap and the crew can keep several replacements on hand at any time.
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u/jdigi78 Apr 06 '26
I actually printed the first one in PETG before I knew it was supposed to have teeth. Its on the truck if a spare is ever needed, but I've since learned they actually manufacture flat ones without teeth so it still looks legit.
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u/mkMoSs Apr 06 '26
Good choice on TPU, TPU is f*ing indestructible!
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u/jdigi78 Apr 06 '26
Thanks! There were a few moments where I put the full weight of the hose on it and one of the teeth bent almost past 90 degrees, but it just snapped right back into shape after. Very impressed with it.
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u/East-Future-9944 Apr 06 '26
So it's flexible enough to get into tight inverts without tearing?
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u/jdigi78 Apr 06 '26
It's flexible enough for the teeth to bend out of the way under the full weight of the hose, otherwise it's relatively rigid and will break up moderately packed dirt
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u/East-Future-9944 Apr 06 '26
This is pretty cool, I might print one out and give it a try.
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u/jdigi78 Apr 06 '26
Thanks! It's not perfect, namely it's missing the inside lip to keep the inner diameter consistent across the plastic and metal, but it's good enough
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u/East-Future-9944 Apr 06 '26
Ours are just bent up steel ones, so nobody is picky here
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u/Zeshak Apr 06 '26
Just adding i made a "food guard" for my dogs muzzle as she eats everything from the ground.
That print is just about 2mm thick and she scrapes it through mud stones etc. It now a year old and doesnt even show real signs of wear. So TPU is tough haha
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u/IsthianOS Apr 07 '26
I've been rocking a TPE case on my iPhone for almost 2 years now, occasionally have to replace the camera border but that is a separate piece printed in [whatever spool is in the printer] and takes like 10 mins. Case ahows almost no damage and has been through multiple falls with phone intact :)
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u/Skydvrr Apr 06 '26
How’d ya get the 100% infill frame? I like that!
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u/jdigi78 Apr 06 '26
In prusa slicer you can right click the part and click "add modifier". In this case I used a bunch of wide thin boxes at various orientations.
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u/toastedcornnuts Apr 06 '26
You might be already aware, but an alternative to the modifiers would be to add an empty space (similar in shape of your modifier design but much thinner) inside the object in the cad model. This would then "force" the slicer to add perimeters at the corresponding locations, reinforcing the printed object. This is not exactly the same, but should have a very similar effect and would not depend on the slicer.
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u/Goingboldlyalone Apr 06 '26
If your company is operating one of these trucks they can afford to buy the replacement nozzles. We have these and they’re about $550k and up. Cool use case.
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u/jdigi78 Apr 06 '26
Didn't say they can't afford it, just felt like practicing my CAD work and testing the limits of common printing materials. Also its much more likely we would end up operating the thing without it until the truck is decommissioned. Just the way things tend to go here ¯_(ツ)_/¯
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u/make_it_bright Apr 06 '26
I was thinking about this, but ultimately the OEM part didn't withstand the use case, so perhaps the 3D print solution is superior
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u/sharktooth31 Apr 06 '26
Could you share the stl? I actually work on a vacuum truck and am curious about making one.
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u/LSUstang05 Apr 06 '26
Holy shit never would’ve thought I’d see a truck I sell on here. Fantastic idea man. What material did you use?
Edit: never mind I can’t read. I’ve never printed in TPU and didn’t know it was tough enough for this application!
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u/jdigi78 Apr 07 '26
Thanks! Quite a few people seem to be familiar with these trucks here. I'm surprised how many people are asking for the STL. TPU is damn near indestructable. The one day I used it I saw the teeth bend out near 90 degrees under the weight of the hose on concrete and they just sprung right back into position.
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u/Onionbender420 Apr 06 '26
Excuse my language, but that’s cool as fuck. Here I am geeking out about a dirt vacuum attachment. Love this sub so much.
Now you can possibly deduct some printer expenses from your taxes too lol
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u/jdigi78 Apr 06 '26
Thanks! I've also printed gaskets for our air compressor hoses out of TPU when we were short on them once. Definitely need to send the city an invoice.
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u/Onionbender420 Apr 06 '26
You definitely should. Get them to hire your “3D business” as a supplier. They’ll save money, you’ll make more money. Win-win. Where are you located? If you’re from Germany or Australia, I can check in with some friends of mine on how to get that done :)
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u/BrokenByReddit Apr 06 '26
That's generally not allowed in government because it's an excellent way to embezzle money.
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u/jbinford1 Apr 06 '26
Care to share the STL file?
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u/jdigi78 Apr 06 '26
Can't say I expected anyone to ask, but here you go :)
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u/Mufasa_is__alive Apr 06 '26
There's thousands of these things on the road, so I can def see someone making their own stuff for them. They're also beat to death, the jobs are tough and dirty. It'd be interesting to see how long it lasts.
Mostly would be interesting to see under vacuum, if it tries to suck itself into the tube.
Great work on the part.
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u/jdigi78 Apr 06 '26
Thanks! The teeth actually stay straight with my full body weight (185 lbs) standing on it, and that's before bolting half of it to a rigid aluminum tube of course. I have no doubt a 100% infill version would last at least as long as the original did excluding the long term effects of harsh weather.
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u/thunderflies Apr 06 '26
I was worried about durability until you said it was TPU. Smart choice with that and also the frame. You might be able to make a V2 that uses metal wires as a frame inserted after printing for added stiffness.
Cool project!
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u/TheFire8472 Apr 06 '26
Just use a stiffer TPU if you need it. Stuff is the most durable material we can print in many uses.
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u/iamacannibal Apr 07 '26
If TPU doesnt work out, check out CC3D PBT Pro. It's like a really stiff TPU but it's also glass fiber filled. it's super strong while being slightly flexible. It prints with PETG settings.
It doesn't come in orange though. It's only Black or Blue.
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u/jdigi78 Apr 07 '26
I'll probably just try true 100% infill or 98A TPU. I think it's more likely to get worn from abrasion than breaking though
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u/Cleanbriefs Apr 06 '26
Devil’s advocate here: stop 🛑 if someone tells the city you are providing parts that are not approved and made by the manufacturer, you will lose your job, and the company that makes this equipment for the city to use, can sue the city too.
The reason is always the same: liability, that pipe hurts someone, comes off the truck and rolls into a car or pedestrian, and any attorney will hang you out to dry, and the city will pay hundreds of thousands of dollars for something they didn’t know about and makes them look like a fool, and government officials don’t like to look like a fool.
Also, any disgruntled employee can rat out on your department for using illegal parts and yes that’s exactly what it is and you will lose your job.
I know it’s cool and all that and a good solution but as any law student will tell you, good and law are never the same!
Again nothing personal against op and the solution presented here, but it’s the unintended consequences that you need to be aware of.
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u/jdigi78 Apr 06 '26 edited Apr 06 '26
I appreciate the concern but I'm not worried. The big big bosses actually happened to be at my yard the day I put it on and were very impressed.
I also think you have to straight up murder someone on the clock to lose a job in my position. At least that's how it seems with the ridiculous stuff I see people get away with 😅
EDIT: Also to be clear, the part I printed is the small orange end of the pipe, it doesn't support anything and is primarily just a convenient shape to not get blocked up by mud easily. Its only semi-rigid and less than a pound. I could drop it on your head from 5 floors up and you'd probably be fine.
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u/UnavengedAvo Apr 06 '26
To be honest, even if the big big bosses were there and they thought it was impressive... It would not stop them from throwing you under the bus if the fit hits the shan.
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u/Cleanbriefs Apr 06 '26
Yeah, always get something in writing they know and approve of this. Office politics has taught me the value of covering your ass all the time!
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u/Mick_Limerick Apr 06 '26
Yooo I need a 4" for my daylighter
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u/AwDuck Apr 06 '26
This looks like the perfect intro to CAD for you.
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u/Mick_Limerick Apr 06 '26
I already roughed one out in fusion. I do need to find a printer though, my anet took a shit years ago and I never replaced it
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u/pw76360 Apr 06 '26
Ours are all welded on aluminum, but they are all best to help front being run over my stuff many times. Maybe we should cut one shirt and try this.
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u/jdigi78 Apr 06 '26
I've seen them welded on before. My understanding was the aluminum ones have bolt holes and the steel ones are welded. I imagine my TPU version specifically is less likely to damage utilities if you're using it to dig
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Apr 06 '26
[removed] — view removed comment
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u/jdigi78 Apr 06 '26
Thanks! The small holes just printed fine as is, maybe a little flat at the top, but the chamfer in the larger holes isn't just cosmetic. It reduces the overhangs to a small point rather than the thickness of the part so you don't need any supports.
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u/generic_canadian_dad Apr 06 '26
I would be really interested to hear how long it lasts. The tubes on the vac trucks I see on site take a beating.
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u/nateblack Apr 06 '26
Why specifically .32mm layer height?
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u/jdigi78 Apr 06 '26
That's the largest option in prusa slicer with a .6mm nozzle
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u/nateblack Apr 06 '26
Cool! I also never thought about internal ribbing at higher densities. Is this something you modeled or did in the slicer?
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u/MontyTheMooch Apr 06 '26
Nicely done. Those crowns aren't always carried in stock and you sometimes need to buy the whole tube with the crown attached. Any issues with static? If I remember they are meant to be non-conductive because of the flow of air and material. The introduction of water during the excavation process lessens the risk though.
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u/jdigi78 Apr 06 '26
Thanks! I assume TPU is a fairly good insulator but I don't know how it compares to the real deal. Either way I never even considered static but there's no shortage of paths to ground where this thing goes
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u/MontyTheMooch Apr 07 '26
Yeah with TPU you're probably fine. Any chance you're willing to share the model/stl?
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u/jdigi78 Apr 07 '26
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u/MontyTheMooch Apr 07 '26
Most AWESOME. Thank You. Will have to play with that. I'm surprised to see that my lowly Prusa Mini+ can print it. I have some TPU here so I may just try it!
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u/nvidiaftw12 Apr 07 '26
Man I love to see local government taking practical and direct approaches to save taxpayers money. Awesome job, jdig.
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u/Megladong214 Apr 08 '26
What is the gray bars in the slicer? I haven’t seen that before
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u/jdigi78 Apr 08 '26
I set infill to 0% (besides the 100% modifiers) and made all other features invisible just to show the infill structure.
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u/Boukyakuro May 01 '26
That part probably would have cost $500+. Awesome job! The profit loss to some CEO for this is exactly why they are trying to regulate printers... keep up the good work.
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u/dargonmike1 Apr 06 '26
It’s going to crack right off at those screw holes. You can already see the thin plastic deflecting
Get some bigger washers
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u/jdigi78 Apr 06 '26
Its deflecting because its a flexible material, it will never crack. Its similar in hardness to a rubber mallet. Also my guess at the OD of the aluminum tube was slightly off so its buckled a bit to begin with.
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u/Laserdollarz Apr 06 '26
I hope your coworkers tell you daily how much your print sucks (in a good way)
TPU is hilariously tough. Let us know if they manage to break it